Q: How many atoms are in $$2.45$$ mol of copper?

$$1.47 \times 10$$^{24}$$ atoms

Question 1

Which statement best describes the Law of Conservation of Mass as it applies to chemical reactions?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 2

Dalton’s Atomic Theory states that all atoms of a given element are identical in mass and properties. Which experiment challenged this postulate?

Accepted Answer

Discovery of isotopes, showing atoms of the same element can have different masses.

Question 3

A sample of water ($$\mathrm{H_2O}) is $$decomposed into 32 g of oxygen and 4 g of hydrogen. What is the mass ratio of oxygen to hydrogen in water?

Accepted Answer

$$8:1$$

Question 4

Which law explains why all samples of a given compound have the same proportions of their constituent elements?

Accepted Answer

Law of Definite Proportions

Question 5

If 10 kg of limestone ($$\mathrm{$$CaCO_3$$}) is $$heated and decomposes into $$\mathrm{CaO}$$, $$\mathrm{CO_2$}$$, and $$\mathrm{H_2O}$$, what must be true according to the Law of Conservation of Mass?

Accepted Answer

The total mass of products will be exactly 10 kg.

Question 6

Which experiment led to the discovery of the electron and showed that atoms are divisible?

Accepted Answer

Thomson’s cathode ray tube experiment

Question 7

What is the charge and relative mass of a neutron?

Accepted Answer

Charge: $$0$$, Relative mass: 1 amu

Question 8

Which model of the atom was proposed after the discovery of the nucleus?

Accepted Answer

Nuclear model

Question 9

A chlorine isotope has 17 protons and 19 neutrons. What is its mass number and chemical symbol?

Accepted Answer

$$\mathrm{^{36}Cl}$$

Question 10

Which statement about isotopes is correct?

Accepted Answer

Isotopes have the same number of protons but different numbers of neutrons.

Question 11

The atomic mass of magnesium is calculated using the masses and abundances of its three naturally occurring isotopes: $$23.99$$ amu ($$79.00\%$$), $$24.99$$ amu ($$10.00\%$$), and $$25.98$$ amu ($$11.01\%). $$What is the atomic mass of magnesium?

Accepted Answer

$$24.31$$ amu

Question 12

Which element is defined by the number of protons in its nucleus?

Accepted Answer

Element

Question 13

Which group in the periodic table contains elements that are mostly unreactive due to their full outer electron shells?

Accepted Answer

Noble gases

Question 14

What is the charge of an ion formed when a sodium atom loses one electron?

Accepted Answer

$$+1$$

Question 15

How many atoms are in $$2.45$$ mol of copper?

Accepted Answer

$$1.47 	imes 10$$^{24}$$ atoms

Question 16

A sample contains $$2.80 	imes 10$$^{20}$$ silver atoms. How many moles of silver atoms are present?

Accepted Answer

$$4.65 	imes 10$$^{-4}$$ mol

Question 17

Which property distinguishes metals from nonmetals on the periodic table?

Accepted Answer

Metals are malleable, ductile, and good conductors of heat and electricity.

Question 18

Which law is demonstrated when two elements form more than one compound and the masses of one element that combine with a fixed mass of the other are in ratios of small whole numbers?

Accepted Answer

Law of Multiple Proportions

Question 19

Which subatomic particle is approximately 2000 times lighter than a hydrogen atom?

Accepted Answer

Electron

Question 20

Which of the following best describes a metalloid?

Accepted Answer

An element that exhibits properties intermediate between metals and nonmetals.

Atoms and Elements: Foundations of Atomic Theory and Structure

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